Method and system for biometric sensing and subcutaneous structure detection

ABSTRACT

A system, apparatus and method for obtaining biometric data from characteristics of a fingerprint and obtaining characteristics of subcutaneous structures that are embedded within finger tissue and located in relation to the fingerprint.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/245,299, filed Jan. 11, 2019, which is a continuation ofU.S. patent application Ser. No. 15/470,465 filed Mar. 27, 2017, whichis a continuation of U.S. patent application Ser. No. 14/174,761 filedFeb. 6, 2014 (now U.S. Pat. No. 9,607,206 issued Mar. 28, 2017), whichclaims benefit of U.S. Provisional Patent Application 61/761,665 filedFeb. 6, 2013, all of which are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

Fingerprinting is one of the most widely used biometric for humanidentification. Identification is obtained by analyzing a givenfingerprint image obtained by a fingerprint sensor for the relativelocations and orientations of structural elements such as branching orending of ridges and valleys known as minutia. These characteristics areobtained in the enrollment mode of a person's finger or multiplefingers. In the verification mode a second fingerprint is obtained andanalyzed for similarity based on minutia or other previously definedfingerprint characteristics. This minutia is also referred to herein asa type of biometric marker.

The probability for false identification either a false acceptance orfalse rejection depends on the number of minutia identified in thefingerprint. The number of minutia increases with the fingertip areabeing scanned. However, for integration of fingerprint sensors intomobile devices for access control, such as cell phone a small areafingerprint sensor is very desirable.

Sonavation, Inc. of Palm Beach Gardens, Fla., USA manufactures biometricsensing devices having a ceramic Micro-Electro Mechanical System (MEMS)piezoelectric array that is made from a ceramic composite material. Whenthis piezoelectric material is formed into a pillar 1/10th the diameterof a human hair, it has a unique set of properties that enable it tomechanically oscillate when an electric field is applied or create anelectrical voltage when mechanically vibrated. The piezoelectric pillaris electrically vibrated at its natural ultrasonic resonant frequency.If a fingerprint ridge is directly above the pillar, much of theultrasonic energy is absorbed by the skin and the signal impedance ofthe pillar is very high. If a valley is directly above the pillar, verylittle energy is absorbed and the impedance is very low. By arrangingthe pillars in a matrix of several thousand elements a two-dimensionalimage of a fingerprint can be created. An imaging ASIC electricallycontrols the pillar oscillation, imaging of the fingerprint and datamanagement of the fingerprint information.

U.S. Pat. No. 7,141,918 describes an biometric sensing device having theabove piezoelectric array operable for fingerprint imaging. It has beenfound as also described in this patent that the piezoelectric array canbe operated in non-fingerprint imaging modes to obtain other biometricinformation, such as in an echo mode to provide imaging, such as bone,or a Doppler-shift mode to detect blood flow velocity and blood flowpatterns. Although the sensor described in this patent is useful, itwould be desirable to also operate the sensing device in athree-dimension ultrasound imaging mode to provide improved imaging ofsubcutaneous structures for use in biometric identification (or medicalapplications) that does not rely on echo mode imaging as described inU.S. Pat. No. 7,141,918.

The discussion above is merely provided for general backgroundinformation and is not intended to be used as an aid in determining thescope of the claimed subject matter.

BRIEF DESCRIPTION OF THE INVENTION

Accordingly, it is an object of the present invention to provide abiometric sensing device having a piezoelectric array providing improvedthree-dimension imaging of subcutaneous tissue structures of a finger,such as bone or vasculature, utilizing pitch/catch ultrasonically formedimages.

It is another object of the present invention to provide a biometricsensing device having a piezoelectric sensor array providing improvedthree-dimension images of subcutaneous tissue structures of a fingerwhere such images are useful for further providing proof of lifeparameters.

Briefly described, the present invention embodies a biometric sensingdevice having an array of piezoelectric ceramic elements operable in afirst mode for producing first data representative of a fingerprintimage, and a second mode for producing second data representative ofleast one three-dimensional image of subcutaneous tissue structure(s),such as or bone or vascular, formed by pitch-n-catch ultrasound imaging.The images provided from operating the sensing device in the first andsecond modes provide anatomical and morphological biometrics (biometricdata) for use in biometric identification.

The second data representative of least one three-dimensional image ofsubcutaneous tissue structure, may also be used for determining elasticproperties of tissue, and vital or proof of life parameters, i.e.physiological information, such as heart beat, blood flow velocities,and pulse wave pattern, or other parameters which can be used todetermine if the finger disposed upon the sensor array is fake or dead.

The elastic properties of tissue which may, like captured fingerprintimage and the one or more images of subcutaneous tissue structure(s),provide biometrics (biometric data) for use in biometric identification.Thus, multiple types of biometric data can obtained with a singleapplication of a finger to the sensor array, which can be done in realtime and simultaneously.

The architecture of the identification device is similar to what isdescribed in U.S. Pat. No. 7,141,918, also referred to herein as the'918 patent. Embodiments of the subject invention include variousimprovements over the '918 patent that are described herein. Theseimprovements include those relating to electronic control and dataacquisition. U.S. Pat. No. 7,141,918 is incorporated herein byreference. Further, U.S. Pat. Nos. 7,844,660, and 6,720,712, which arerelated to U.S. Pat. No. 7,141,918 are also incorporated herein byreference.

This brief description of the invention is intended only to provide abrief overview of subject matter disclosed herein according to one ormore illustrative embodiments, and does not serve as a guide tointerpreting the claims or to define or limit the scope of theinvention, which is defined only by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features of the invention can beunderstood, a detailed description of the invention may be had byreference to certain embodiments, some of which are illustrated in theaccompanying drawings. It is to be noted, however, that the drawingsillustrate only certain embodiments of this invention and are thereforenot to be considered limiting of its scope, for the scope of theinvention can encompass other equally effective embodiments.

The drawings are not necessarily to scale. The emphasis of the drawingsis generally being placed upon illustrating the features of certainembodiments of the invention. In the drawings, like numerals are used toindicate like parts throughout the various views. Differences betweenlike parts may cause those parts to be indicated with differentnumerals. Unlike parts are indicated with different numerals. Thus, forfurther understanding of the invention, reference can be made to thefollowing detailed description, read in connection with the drawings inwhich:

FIG. 1A is a schematic diagram of a top down view of a piezoelectricidentification device according to the present invention; FIG. 1B is aside perspective view of the piezoelectric identification device inwhich pillars (elements) are evenly spaced and are separated by fillermaterial.

FIG. 2 a schematic illustration of the sensor array addressing scheme isshown, where there are M and N number of elements 11, disposed in M rowsalong an x axis and in N columns along a y axis.

FIG. 3 illustrates an identification device that is coupled to acomputer system.

FIG. 4 illustrates a cross-section of sensor array 10 and of a finger 30placed proximate to an upper surface of the sensor array so that thefinger's surface 31 is in direct contact with its protective shield 23.

FIG. 5 illustrates a scan aperture 40 that is scanned by processor 13with respect to an x axis (M rows) and y axis (N columns) dimensions ofthe scan aperture, like shown in FIG. 2.

FIG. 6A illustrates a transit aperture 41 that is selected by processor13 to form a transmit beam or pulse 46 (shown as a translucent volume)having an hour-glass shape, having 6 transmit channels. FIG. 6Billustrates transmit signals traveling via channels A-F.

FIG. 7A illustrates a receive aperture 42 selected by processor 13 toreceive acoustic energy (beam or pulse 49). FIG. 7B illustrates transmitsignals received via channels A-F.

FIG. 8 illustrates a combined output signal 54.

FIG. 9 illustrates ultrasound scanning of a blood vessel 50 within afinger via a sensor array.

FIG. 10 illustrates ultrasound scanning of a bone structure within afinger via a sensor array.

FIG. 11 illustrates operation of the identification device 9 of FIG. 3while scanning a finger via a sensor array, like shown in FIGS. 4, 9 and10.

FIG. 12 is a simplified illustration of sensor control hardware andsoftware.

FIG. 13 illustrates an alternative hardware for transmitting andreceiving signals to and from the sensor array.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1A, a schematic diagram of a the piezoelectricidentification device 9 according to the present invention is shown.Identification device 9 has a sensor array 10 of piezo-electric elements11 providing mechanical resonator sensing, a sensor input signalgenerator 12, and a processor 13. Under control of processor 13, theinput signal generated by input signal generator 12 is coupled to sensorarray 10 by a signal multiplexer 15 a, and output signal of sensor 10 iscoupled to processor 13 by a multiplexer 15 b.

Processor 13 processes the output signals from select element(s) viamultiplexor 15 b to obtain biometric data which may then be stored in amemory 14. Biometric data can include one or more fingerprint images,and/or one or more ultrasound images of subcutaneous structures of thefinger, subcutaneous tissue parameter(s) such as of tissue elasticity,and/or detected proof of life parameters, as described later below.Addressing of elements 11, via multiplexers 15 a and 15 b, is enabledvia a mux controller 16 in accordance with user specified imaging modesand/or in detection of proof of life parameters. Although eachmultiplexor 15 a and 156 is shown singularly, each multiplexor'sfunction may alternatively be designed to be provided by two or moremultiplexors as desired.

Sensor array elements 11 may be of lead zirconate titanate (PZT) orother material having similar properties, preferably, PZT 1-3 composite.The piezo-ceramic elements 11 can have shapes other than rectangular,such as circular as shown in FIG. 2. Sensor area 10 is preferablyprovided on a support layer, such as described in the above incorporatedpatent. Other ASIC chips may provide the electronics shown in FIG. 1A towhich the sensor is connected.

A more detailed view of sensor array 10 is shown in FIG. 1B in whichelements 11 represent evenly spaced pillars with filler material 17there between. Filler material 17 may be an epoxy or polymer havingmicro-spheres. Transmit electrodes (or lines) 19 and receive electrodes(or lines) 20 (See FIG. 1A) are provided above and below, respectively,along sensor array 10. Over the transmit electrodes 19 is a shield orprotective coating layer 22, such as urethane providing a surface 23upon which a fingertip may be placed. Below the receive electrodes 20 isa support substrate 24, such as of foam material.

Referring to FIG. 2, a schematic illustration of the addressing schemeis shown, where there are M by N number of elements 11, disposed in Mrows along a horizontal x axis as shown and in N columns along avertical y axis as shown. For example; M and N may equal 368 and 256,respectively, but another number of elements, and row and columngrouping thereof, can be employed in accordance with other embodimentsof the invention. Transmit electrodes 19 are parallel conductors thatconnect to the top of elements 11 in rows 1 to M, while receiveelectrodes 20 are parallel conductors that connect to bottom of elements11 in columns 1 to N. In accordance with some embodiments, each element11 is 40 microns square by 100 microns deep, thereby yielding a densesensor array 10 having a 20 MHz fundamental frequency sonic waveelements 11. A spacing of 10 microns is used between elements 11 and ispreferred in order to provide a 50-micron total pitch between elements.Other geometries may be used, such as for example, a pitch of greater orlower than 50 microns. For example, a sensor with 368 rows and 256columns may be 18.7 by 13 mm, or other size according to the maximumimaging size desired for the particular application.

In some embodiments, sensor array 10 may be manufactured as described inU.S. Pat. No. 7,489,066, which is herein incorporated by reference. Byarrangement of the elements in an array of rows and columns, elements 11are individually addressable for application of an input signal by row,and then addressable for reading out an output signal by column, byselection of electrodes 19 and 20, via multiplexors 15 a and 15 b,respectively.

A ground switch 26 is provided coupled to all transmit electrodes 19between edge connector 19 a and multiplexor 15 a enabling processor 13to connect electrodes 19 to ground when needed. Similarly, a groundswitch 27 is provided coupled to all receive electrodes 20 between edgeconnector 20 a and multiplexor 15 b enabling processor 13 enablingprocessor 13 to connect electrodes 20 to ground when needed. The benefitof ground switches 26 and 27 is that it avoids additional switching ofground and signal electrodes as described in U.S. Pat. No. 7,141,918,thereby avoiding unwanted additional capacitive loads parallel to thetransmitting and receiving elements 11.

As will be described below, processor 13 is programmed within itsembedded memory (or memory 14) to enable all sensing operations bysensor array 10 as described herein, including at least fingerprintimaging, and three-dimensional ultrasound imaging. Further, processor 13may provide other activities commonly implemented in an ultrasonicimaging system as part of electronic beam formation including syntheticaperture imaging.

Referring to FIG. 3, identification device 9 is coupled to a computersystem 28 for data communication to send commands and receive biometricdata from identification device 9. Computer system 28 may be anymicroprocessor-based device operating in accordance with a program orinstructions which utilizes identification device 9 to obtain biometricdata via sensor array 10 as needed for identification (e.g.,verification and/or enrollment) of biometric data. Such computer system28 uses biometric data connected from the sensor to enable biometricfeature or identifier matching in accordance with a database or memorywithin system 28, or accessible to system 28. For example, computersystem 28 may be part of portable identification device, point oftransaction system, or any other device requiring secure biometricsensing to enable access to physical and/or electronic resources.

Identification device 9 is operable in a fingerprint imaging mode, and athree-dimensional subcutaneous tissue structure imaging mode, asdescribed below.

Fingerprint Imaging Mode.

FIG. 4 illustrates a cross-section of sensor array 10 of the device 9,and a finger 30 placed proximate to the sensor array so that thefinger's surface 31 is in direct contact with its protective shield 23.The finger's Such surface 31 has ridges 32, which make such directcontact, and valleys 33 which do not make such direct contact with theprotective shield 23. When an element 11 is driven at a resonantfrequency by the input signal generator 12, via one of transmitelectrodes 19 selected by mux controller 16 via multiplexor 15 a, itsoscillation is directed or transmitted towards the finger's surface 31and produces a sonic wave either towards ridges 32 or valleys 33 asgraphically illustrated by sonic waves 35 and 36, respectively. Theinput signal excites elements 11 within the sensor array 10 and causesthese elements to oscillate, preferably at a resonant frequency.Phenomena outside of the sensor array 10, such as a presence of acousticimpedance or a reflection of acoustic energy off of outside entities(external to the sensor), further influences the motion of theseelements 11 (apart from the influence of input signal excitation) withinthe sensor array 10. Such outside influenced motion is monitored,measured and analyzed by electronic hardware in combination withsoftware that controls operation of the electronic hardware. (See FIG.12)

The surface 31 response to sonic wave differs due to contact to tissueof a ridge versus non-contact of valley difference in impedance (orattenuation/voltage) which is detectable by the same element 11 whichtransmitted the sonic waves or beam, via one of receive electrodes 20selected by mux controller 16 via multiplexor 15 b, thereby providing ameasure as to whether the element is facing a ridge or a valley. Theprocessor 12 builds a map in memory 14 where each element response(output signal) detected by processor 12 represents one pixel of thetwo-dimensional fingerprint image in memory 14, where each pixel may berepresented as a black or white value to represent a ridge or valley,respectively, or vice versa. Thus, read out in which of impedancemeasured is converted into a fingerprint image of ridges and valleys.

Such operation of identification device 9 to obtain a fingerprint imageis described in more detail in connection with FIGS. 17-22 of inincorporated U.S. Pat. No. 7,141,918 which is included in Appendix A ofthe prior filed provisional patent application, or other U.S. Pat. Nos.7,489,066, 7,514,842, 8,331,633, and 8,335,356 which are also all hereinincorporated by reference.

Preferably, sensor array 10 operates to obtain a fingerprint bydetecting the impedance at a resonant frequency of an applied inputsignal generated 12, via multiplexor 15 a, where upon soon after adriving input signal of each element 11 ceases in time, and an outputsignal is read from that same pixel. That output signal isrepresentative of impedance. In other words, the element 11 ring(vibration) characteristic causes an electrical output signal to beproduced by the element that when sampled, via multiplexor 15 b,provides a measure of impedance. Further, two impedance measurements cantake place at two different frequencies (e.g., 19.8 MHz and 20.2. MHz)for each element 11, where the difference of measured impedance at eachfrequency is used to determine whether the element 11 is facing andadjacent to a ridge or a valley as described in incorporated U.S. Pat.No. 7,141,918.

Ultrasound (Pitch/Catch) Three Dimensional Imaging Mode.

Identification device 9 can also operate sensor 10 in a pitch/catchimaging mode to obtain three-dimensional ultrasound images within afinger presented to sensor array 10. Thus, a sensor principallydescribed for fingerprint image capture can enable viewing of structureswithin the same tissue that provided a fingerprint image, such asvascular structures (venous and arterial vessels), or bone structure. Asdescribed in more detail below, processor 13 operates the elements 11 ofthe sensor array 10 in this pitch/catch mode by connecting thetransmitter and receiver in series, rather than in parallel as in echoimaging of the prior incorporated U.S. Pat. No. 7,141,918.

As illustrated in FIG. 5, an scan aperture 40 is scanned by processor 13along in x and y axes or dimensions, where the x dimension correspondsto the 1 to M rows, and y dimension corresponds to the 1 to N columns ofFIG. 2. The scan aperture 40 is formed along the intersection of a groupof “m” number of adjacent rows of elements 11 activated by processor 13to provide a transmit aperture 41 that produces a transmit beam, and agroup of “n” number of adjacent columns of elements 11 activated byprocessor 13 to provide a receive aperture 42 that receives a receivebeam, where the time delay of signals received is representative ofstructure(s) in the volume of tissue into which the transmit beam isfocused and the receive beam is received above scan aperture 40.

During scanning, processor 13 moves the scan aperture 40 along the x andy dimensions by selecting different groups of “m” rows and “n” columnsin which to overlap and form different scan apertures 40. For beamfocusing, the transmit electrodes 19 to the “m” rows of elements 11 aredivided equally into “p” number channels, where the number of transmitchannels equals “m” divided by “p”. Similarly, the receive electrodes 20the “n” columns of elements 11 are divided equally into “r” number ofreceive channels, where the number of receive channels equals “n”divided by “r”. An example for one of the multiple scan apertures 40that may take place during scanning of vasculature within the tissueabove sensor array 10 during scanning of multiple different scanapertures is shown in FIGS. 6A and 6B, where FIG. 6A represents atransmit cycle and FIG. 6B represents a receive cycle.

In FIG. 6A a transmit aperture 41 is selected by processor 13 to form atransmit beam or pulse 46 (shown as a translucent volume) having anhour-glass shape. In this example, “m” equals 12 and “p” equals 6,resulting in 6 transmit channels A-F each with two rows. In order tofocus the beam along a volume 48 of the transmit beam 46 at a distancebelow the tissue surface, the transmit (input) signal is applied bytransmit channels A-F and offset in time in accordance with distance ofrows from a location in volume 48. The transmit signal is first appliedto rows of the most outer transmit channels A and F first, then thesecond most outer transmit channels B and E, and then the central mosttransmit channels C and D last, as illustrated in FIG. 6B.

Thus the transmit aperture 41 forms a transmit beam 46 which will arriveat approximately the same time thereby focusing transmit beam 46 atlocations in the intended volume 48 that may contain the object orstructure of interest, such as a blood vessel 50. In forming transmitbeam 46 all other rows of elements 11 which are not used in the transmitaperture 41 are inactive. A blood vessel may or may not be fullyincluded in the transmit beam 46. During this transmit cycle, switch 27is switched to ground by processor 13 to ground the receive electrodes20, while switch 26 is not set to ground.

After transmit beam 46 is launched into the tissue of the finger 30 andan additional period for ring down of the transmit electrodes 19transmitting elements 11 along the “m” rows (i.e., their electrodes 19)are switched to ground by processor 13 via switch 26, and while switch27 is not set to ground. The receive cycle can then begin.

FIG. 7A shows an example of the receive aperture 42 selected byprocessor 13 to receive beam or pulse 49 having an hour-glass shape. Inthis example, “n” equals 12 and “r” equals 6, resulting in 6 receivechannels A-F each with two columns. In order to focus receiving beamalong a volume 52 beam the tissue surface, the receive (output) signalis read (or detected) from receive channels A-F, and read offset in timein accordance with distance of columns from a location in volume 52. Thereceive signal is first read from columns of the most outer receivechannels A and F first, then the second most outer receive channels Band E, and then the central most receive channels C and D last, asillustrated in FIG. 7B.

Thus the beam received by elements 11 of the receive aperture 42 willarrive at approximately the same time from the intended volume 52, whichin this example includes part of blood vessel 50. The signals from allthe receive channels A-F are aligned in accordance with the time offsetof reception shown in FIG. 7B and combined by a beam former 53 inprocessor 13 to form a combined output signal for scan aperture 40 asshown in FIG. 8.

In receiving the output signals from receive channels A-F, all othercolumns of elements 11 which are not in receive aperture 42 areinactive. Receive beam 49 is orthogonal to the transmit beam 46, and itis their intersection along transmit aperture 41 and receiver aperture42 which defines the effective pitch/catch scan aperture 40.

The processor 13 receives signal from the “n” column of elements 11during the sampling interval associated with the round trip time afterthe ceased transmit beam is backscatter reflected towards the sensor 10,from the objects or structures desired to be imaged. The delay in timeof the combined output signal from beam former 53 over the samplinginterval represents distance from the sensor array 10, and the amplitudeor value 54 of the signal at different depths along the z dimensionsampled during the sampling interval is recorded by processor 13 inmemory 14 at x,y,z coordinates associated with that scan aperture 40.The processor 13 may receive combined output signal over the entiredepth of the scan aperture 40, but records information in memory 14 overa desired range of volume's depth of intersecting volumes 48 and 51 ofscan aperture 40 to provide a three-dimensional ultrasound imageindicating structures of interest which can be within that desired depthrange from sensor array 10.

FIG. 8 shows an effect upon a beam formed signal by a blood vessel 50along the z axis at a distance from sensor 10 centered along the scanaperture 40, where +/− amplitude value 54 of coordinate along the x axisat a common y position centered about the receive aperture 42. (Theamplitude of the signal between the outer boundaries of the vesselsdiameter may also be processed by processor 13 to provide velocityinformation of the flow there through at that x, y coordinate for use asa vital parameter). In other words, this transmit beam 46 is steered intwo orthogonal axes x and y within a two-dimensional (2D) scan of thesensor array 11. The 3rd axis, defined as the axial or z-axis isobtained by time of arrival analysis of subcutaneous tissue causingbackscattered sound waves by processor 13.

The processor adds the information at sampled points of amplitude 54obtained along the z axis from sensor 10 at the x,y coordinate to a mapin memory 14 along the x and y dimensions thereby building athree-dimensional ultrasound image of subcutaneous structures. A full 20x,y image along an x,z plane is obtained from time history in z andreceive aperture 42 position in y. In other words, this 20 imageprovides a slice along the x,z plane of the full 3D volume presentationof backscattered ultrasound for a given scan aperture 40. Scanning alongthe x axis while scanning the receive aperture for each new positioncreates the full volume representation of the fingertip object. Duringthis receive cycle, switch 26 is switched to ground by processor 13 toground the transmit electrodes 19, while switch 27 is not set to ground.

The processor 13 then repeats the process for different scan apertures40 along the x any y dimensions over the volume of tissue above sensorarray 10 providing multiple slices along x,z planes of scan apertures tocomplete a three-dimensional ultrasound image of subcutaneousstructures.

Three-dimensional beam forming for ultrasonic imaging is described in C.E. Demore et al., Real Time Volume Imaging Using a Crossed ElectrodeArray, IEEE UFFC Trans vol. 56 (6) 1252-1261, but heretofore has notbeen provided by a sensor array of piezoelectric elements.

As describe above, there is grounding of transmit electrodes 19 andreceive electrodes 20 alternating with receive and transmit cycles foreach scan aperture 40. As vascular structures and bone structures are atdifferent depths in the tissue with respect to sensor 10, the samplinginterval for the subcutaneous tissue may be set to providethree-dimensional ultrasound image of the vasculature of finger 30 asillustrated in FIG. 9, or bone structure of finger 30 as illustrated inFIG. 10, thereby enabling three-dimensional imaging of different typesof subcutaneous structures. Other structures in the tissue of the fingermay similarly be imaged as desired.

Unlike in fingerprint mode where only one transmitting element 11 isused at a time, in the ultrasound pitch and catch mode a subgroup of “n”adjacent transmitters (transmitting elements 11) is active providing anelectronically focused beam 46 in one lateral direction commonlyreferred to as azimuth axis. In the orthogonal direction, commonlyreferred to as the elevation direction, the receive aperture 49 isselected as a sub-group of “m” electrodes 20 via the multiplexer 15 b,thus the effective aperture for transmit and receive becomes the spatialintersection between transmit and receive apertures 41 and 42,respectively. Only a sub-group “m” of the M receive electrodes 20 areconnected via a multiplexer 15 b to a group of “m” receive amplifiersand signal processing chains for beam formation and further backscatteranalysis by processor 13.

In the fingerprint mode all available M receive channels utilized inparallel providing maximum speed for data acquisition. All electrodesare connected to a programmable signal from processor 13 to groundswitches 26 and 27. Thus in the ultrasound imaging mode the receiveelectrodes 19 are grounded during the transmission cycle or phase, butswitched off from ground (unwounded) during the receive phase duringwhich all transmitting elements 11 are grounded.

By analyzing changes in two or more ultrasound images at a x,y,zcoordinate(s) in a blood vessel, proof of life parameter(s) aredetectable, such as velocity or flow of cells through the vessel,heartbeat, or flow patterns, as desired, in a manner as commonlydetected in typical ultrasound imaging system.

Referring to FIG. 11, the operation of an identification device 9 willnow be described for identification (or verification) or a subject'sfinger 30 as presented to sensor array as shown in FIGS. 4, 9, and 10.First, in fingerprint image mode sensor array 10 is operated processor13 to capture an image (two dimensional representation) of a fingerprintalong the surface of finger 30 (step 60), as described above, which isstored in memory 14 as minutia (biometric fingerprint identifiers) inrelative and local sensor x,y coordinates (step 64). Optionally, or inaddition, the fingerprint image may be stored in memory 14, and/or sentto computer system 28.

Next, identification device 9 is switched to three-dimensionalultrasound/volumetric imaging mode. An image of subcutaneous fingertipvascular structure of finger 30 is then captured in memory 14 (step 61),and processed by processor 13 to obtain biometric data of identifiersuniquely characterizing curvature and/or shape of all or majorsubcutaneous vascular structure of the finger in relative and localsensor x,y,z coordinates (step 65). Other tissue characteristics fromimage may also provide biometric identifiers, such as tissue speckle.Optionally, or in addition, the three-dimensional ultrasound image maybe stored in memory 14, and/or sent to computer system 28.

At step 62, subcutaneous tissue parameters are measured from theultrasound image stored in memory 14. The ultrasound image may beprocessed by processor 13 to determine elastic properties of tissue byapplying pressure to the fingertip and estimating the strain in thetissue using typical ultrasound elastography. Reversely, with knowntissue elasticity applied pressure is estimated from tissue strain. Theelastic measure represents another biometric identifier stored in memory14.

The processor 13 using the three-dimensional ultrasound image from step61 stored in memory 14 determines one or more vital parameters which maybe used to reduce the risk that the subject's finger in fake or dead,such as blood flow, vessel wall pulse waves and heart rate parameters.Each of the one or more vital parameters are compared with one or morethresholds stored in memory 14 (or by computer system 28 if sentthereto) which if not met indicates that the subject's finger 30 may befake or dead. Blood flow may be identified using common procedure ofultrasonic flow detection, such as described in J. A. Jensen, Estimationof Blood Flow using Ultrasound, Cambridge University Press, 1996, or R.S. C. Cobbold, Foundations of Biomedical Ultrasound, Oxford UniversityPress, 2007. In addition to identifying blood flow, blood mean velocityor maximum velocities as well as flow spectra are obtained. Heart rateand vessel wall motion is detected from lower frequency variations ofpulsed and continuous wave ultrasound.

An image of subcutaneous fingertip bone structure is then captured andstored in memory 14 (step 63), and processed by processor 13 to obtainbiometric data of identifiers uniquely identifying subcutaneous bonestructure of the finger in relative and local sensor x,y,z coordinates(step 65). Finger bone structure is useful as biometric, particularly ifbone curvature or other bone shape identifiers.

The identifiers of biometric data from finger print, vascular image,bone structure image, and elastic parameter, and provided along withdetermine proof of life parameters to computer system 28 at step 66.Computer system 28 stores a database of security identificationinformation of previously captured identifiers of biometric data offingers of enrolled subjects, and attempts to map the identifiers ofbiometric data obtained from the finger at steps 60-63 to such securityidentification information (step 66). A score is calculated for eachattempted mapping (step 67) and when one of the mapping store exceeds athreshold level identification may be considered as being confirmed. Useof additional biometric data identifier than a finger print for a smallarea subcutaneous biometric image increases the probability for trueacceptance and true rejection.

If the processor 13 (or computer system 28) detects that one or more ofthe proof of life parameters is outside their respective acceptablethreshold values(s) stored in memory 14, the identification process endsand the operator of computer system 28 notified.

Optionally, or in addition, the fingerprint, and/or one or more of thethree-dimensional ultrasound images of vasculature and bone structuremay be stored in memory 14, and/or sent to computer system 28 forstorage in its memory, Further, all or part of the processing ofimage(s) by processor 13 to provide biometric identifiers may beperformed by computer system 28 upon such image(s) if so provided tosystem 28, which like processor 13 operates in accordance with a programor software in its memory enabling such operations.

To enroll a subject rather than for verification, steps 60-65 are alsoperformed, and the biometric data from such steps is sent to computersystem 29 for storage in a database of security information of computersystem 28 along with other inputted identification information relatedto the subject, e.g., name, facial picture, department, etc., for futureuse in biometric identification in a manner typical of fingerprintidentification systems. If the processor 13 (or computer system 28)detects that one or more of the proof of life parameters is outsidetheir respective acceptable threshold values(s) stored in memory 14, theenrollment process ends and the operator of computer system 28 notified.

The identification device 9 may provide other imaging or vital parameterdetection. For example, a very large aperture 40 unfocused beam(transmit and received channels are not time shifted) may be utilizedfor detecting heartbeat. From the heart beat a wavelet (time frequencypattern) may be constructed by processor 13. This wavelet is thenutilized to identify areas of pulsation associated with arterial bloodflow supporting biometric identification by providing temporalfiltering. Further, parallel overlapping transmit and receiving beams,and non-overlapping parallel transmit and receive beams, rather thanorthogonal as described above, may be used, such as useful for detectingand monitoring flow of correlation in three dimensions.

Although the scan aperture 40 is described as being fixed in size alongx and y dimensions, a search for subcutaneous features using a variableaperture may be used, where areas of subcutaneous biometric is firstcoarsely scanned using wider beams; only identified areas by processor13 are scanned using high resolution scanning of smaller scan apertures,such as described above in connection with FIGS. 5 to 8. Identifiedareas may be identified by have pixel values (or spatial distributions)above threshold value(s) indicative of possible object detection.

One or multiple ultrasound three dimensional images described herein maybe analyzed using any common ultrasound analysis to provide additionalbiometric or medical information. Thus, application of biomedicalultrasound to the fingertip may be used for extracting anatomical,morphological and physiological properties of tissue; each one canincreases the number of biometrics used for personal identification andproof of life. Ultrasound images provided from sensor 10 althoughdescribed for identification may be used for medical applications in amanner as typical of ultrasound images.

FIG. 12 is a simplified illustration of sensor control hardware andsoftware. As shown, a central processing unit (CPU) 13, also referred toherein as the processor 13, is electronically attached to a system bus70, also referred to herein as the bus 70. Memory 14, a signal generator12, a controller 16 and a signal processor 76 are also electronicallyattached to the bus and addressable by the processor 13, via the bus 70.The memory 14, represents memory implemented as one or more memorycomponents that are addressable from the processor 13, via the bus 70.Preferably and in some embodiments, the processor 13 can address othermemory components that are not necessarily electrically attached to thebus 70, and are addressable via means other than the bus 70.

Virtual memory 72, represents processor addressable and accessiblememory, whether implemented as memory 14 or as other non-bus attachedmemory. The virtual address space 74 stores digital logic expressed asCPU instructions and processor addressable data. Sensor control software74, is stored within the virtual memory 72, and is configured to controltransmission of signals, and configured to control reception of signalfrom, the sensor array 10 via the processor 13, the controller 16, thesignal generator 12 and the signal processor 76.

In some embodiments, the controller 16 interfaces with multiplexors(“muxes”), like the multiplexors 15 a-15 b shown in FIG. 1A. Because theprocessor also interfaces with the controller 16 via the bus 70, thesensor control software 74 via the processor 13, also exercises controlof the multiplexors 15 a-15 b, via the controller 16.

In other embodiments, as shown in FIG. 13; the controller 16 interfaceswith non-multiplexor based hardware, to transmit and receive signals toand from the sensor array 10. Because the processor also interfaces withthe controller 16 via the bus 70, the sensor control software 74 via theprocessor 13, exercises control of the non-multiplexor based hardwarevia the controller 16.

The sensor control software 74 is configured to operable in a first modefor obtaining a first set of data encoding at least one two dimensionalimage of a fingerprint of a finger. The software 74 is also configuredto be operable in a second mode for obtaining a second set of dataencoding at least one three-dimensional representation of one or moresubcutaneous tissue structures that are located within tissue that isembedded within a finger.

Further, the software identifies biometric information, such asbiomarkers, within both the fingerprint and subcutaneous tissue that isembedded within the finger. Besides minutia, other biomarkers include anearest three dimensional coordinate of a vascular structure, or a bonestructure, relative to one selected fingerprint minutia location. Therelative location between these biomarkers are represented by threedimensional Cartesian coordinates. In other embodiments, other metrics,such as those employing angles and distances, are employed to quantify arelative location between biomarkers within a fingerprint, withinsubcutaneous tissue and/or between a fingerprint and subcutaneoustissue.

With respect to vascular and bone structures, location coordinates ofpoints along an outer surface and/or a center point along anintersecting plane to the vascular or bone structure, are determined andrecorded as a biometric marker.

In some embodiments, after an initial mapping of biomarkers within avascular subcutaneous structure, a second, third and possibly a fourthmapping of one or more biometric markers over time, to identify dynamicproperties of portions of subcutaneous tissue.

For example, locations of biomarkers that change over time, such asthose associated with the vascular structure can be recorded andanalyzed to determine a pattern of motion indicative of a presenceand/or frequency of a heart beat and to optionally determine an amountof blood flow or a pulse wave pattern through the vascular structure,Such analysis can also determine elastic properties, such as anexpansion and contraction measurement of the vascular structure.

Aside from measurement of dynamic properties of biometric markers withinsubcutaneous tissue, a static representation of less dynamic, andrelatively static biometric markers within the finger print andsubcutaneous tissue are measured and combined to represent an overallstatic biometric characteristic of a person, for which is employed forlater comparison with biometric information later obtained from anunidentified person, to perform biometric matching.

In some embodiments, biometric matching involves computation of amatching score. If such matching score equals or exceeds a minimum scorevalue, then an identity match has occurred and as a result, it is highlylikely that a person currently having an un-proven identity, is a personfrom which biometric data has been previously obtained from andregistered and later matched in association with the system of theinvention.

Likewise, if such a matching score is less than a minimum score value,then an identity match has not occurred and as a result, it is notlikely that a person currently having an non-proven identity, is aperson from which biometric data has been previously obtained from andregistered in association \with the system of the invention.

FIG. 13 illustrates an alternative hardware for transmitting andreceiving signals to and from the sensor array 10. A schematic diagramof a top down view of a piezoelectric identification device, accordingto an alternative embodiment of the present invention is shown.

As shown, multiplexors 15 a-15 b are replaced with non-multiplexor basedelectronic hardware components 85 a-85 b, respectively. The component 85a, includes CMOS drivers and is configured for facilitating transmissionof signals from the signal generator 12 to the elements 11 of the sensorarray 10. Use of multiplexors adds significant and unwanted capacitance,which degrades use of the sensor array 10 when generating ultrasoundacoustic energy from the sensor array 10.

The non-multiplexor based electronic hardware 85 a, instead employs CMOSdrivers for periodically switching the transmission of signals to thesensor array 10, instead to a ground potential, when the component 85 b,is receiving signals from the sensor array 10. Likewise, thenon-multiplexor based electronic hardware 85 b, instead employspre-amplifiers for receiving signals and periodically switching thereception of signals from the sensor array 10, to a ground potential,when the component 85 a is transmitting signals to the sensor array 10.

In other words, the receiving (Rx) lines 20 are clamped to ground duringsignal transmission over the (Tx) lines 19, and the transmitting (Tx)lines 19 are clamped to ground while receiving signals over the (Rx)lines 20. This allows for a ground potential clamping multiplexor (mux)on low impedance receiving (Rx) lines during the signal transmission(Tx) sequence and for controlling the transmission (Tx) driver to clampthe transmission (Tx) tines during the signal receiving sequence. Hence,although such a clamping multiplexor (mux) can be employed within 85a-85 b, these components 85 a-85 b are substantially implemented fromnon-multiplexor electronic hardware components, and as a result, arereferred to herein as non-multiplexor based hardware.

In other embodiments, H-bridge transmission drivers can be employed, bychanging the receive (Rx) clamping multiplexor (mux) to an inversepolarity driven transmission (Tx) driver. In this type of configuration,the second transmission (Tx) driver on the (Rx) lines would be placedinto a tri-state during signal (Rx) reception, while the oppositetransmission (Tx) driver would clamp to ground potential.

From the foregoing description it will be apparent that there has beenprovided an improved biometric sensing devices, and systems and methodsusing same for biometric identification. The illustrated description asa whole is to be taken as illustrative and not as limiting of the scopeof the invention. Such variations, modifications and extensions, whichare within the scope of the invention, will undoubtedly become apparentto those skilled in the art

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

What is claimed:
 1. A sensor comprising: an ultrasonic sensor arrayincluding a plurality of sensing elements; a control unit configured forcontrolling, in association with the plurality of sensing elements,transmission of ultrasonic signals to a finger of a person in physicalcontact with the sensor and reception of amplitude signals associatedwith the plurality of sensing elements in the ultrasonic sensor array;and a 3D representation forming unit configured for obtaining athree-dimensional representation of a subcutaneous structure inside thefinger based on the amplitude signals received at respective receivingtimes, wherein the amplitude signals and their respective receivingtimes are reflective of the subcutaneous structure and at least oneparameter thereof.
 2. The sensor of claim 1, wherein the control unit isconfigured for controlling a first set of electrical connections withrespect to the transmission of the ultrasonic signals and a second setof electrical connections with respect to the reception of the amplitudesignals.
 3. The sensor of claim 2, wherein the first set of electricalconnections are connected to a first set of sensing elements of theplurality of sensing elements, and the second set of electricalconnections are connected to a second set of sensing elements of theplurality of sensing elements.
 4. The sensor of claim 3, wherein thefirst set of electrical connections is orthogonal to the second set ofelectrical connections.
 5. The sensor of claim 1, wherein a first set ofthe amplitude signals corresponding to 3D positions of a boundary of thesubcutaneous structure is greater than a second set of the amplitudesignals corresponding to a 3D position internal or external to thesubcutaneous structure.
 6. The sensor of claim 1, wherein the controlunit configured to operate the ultrasonic sensor array in a first modeor a second mode, wherein in the first mode, the control unit isconfigured to obtain a two-dimensional representation of the fingerbased on acoustic energy transmitted and received by the sensingelements of the ultrasonic sensor array, and in the second mode, thecontrol unit is configured to obtain the three-dimensionalrepresentation.
 7. The sensor of claim 1, wherein the subcutaneousstructure is a bone structure within the finger.
 8. The sensor of claim1, wherein the subcutaneous structure is a vascular structure within thefinger.
 9. The sensor of claim 1, wherein the three-dimensionalrepresentations of the subcutaneous structure are used to determine adynamic property of the subcutaneous structure.
 10. The sensor of claim1, wherein the dynamic property includes an elastic property of thesubcutaneous structure.
 11. The sensor of claim 1, wherein the dynamicproperty is used to determine liveness of the person.
 12. The sensor ofclaim 11, wherein the dynamic property is used to measure a heartbeat.13. The sensor of claim 11, wherein the dynamic property is used tomeasure a blood flow through a vascular structure.